Apparatus for processing sheet-metal workpieces

CROSS-REFERENCES TO RELATED APPLICATIONS

0001This application claims the priority of German Patent Application, Serial No. 10 2016 002 765.7, filed Mar. 5, 2016, pursuant to 35 U.S.C. 119(a)-(d), the disclosure of which is incorporated herein by reference in its entirety as if fully set forth herein.

BACKGROUND OF THE INVENTION

0002The present invention relates to an apparatus for processing sheet-metal workpieces.

0003The following discussion of related art is provided to assist the reader in understanding the advantages of the invention, and is not to be construed as an admission that this related art is prior art to this invention.

0004An apparatus for forming a sheet-metal workpiece involves for example a press having a press tool, e.g. a forming tool, which includes a bottom die and a top die between which a sheet-metal workpiece is placed and shaped. When the press tool executes an idle stroke in the absence of a sheet-metal workpiece, there is a risk that the bottom and top dies impact one another, causing damage to the tool and in particular to the effective surface areas. This can happen, regardless as to the type of press, i.e. whether the press is operated mechanically or hydraulically.

0005It is also known to attach so-called rigid distance keepers to the outside of a press tool in an attempt to distance bottom and top dies or their effective surface areas in the lower dead point from one another, when the press tool is run in. As these distance keepers are rigid and thus remain fixed in place. During a working stroke, these rigid distance keepers have to absorb up to 40% and more of the pressing force.

0006It would be desirable and advantageous to provide an improved apparatus for processing sheet-metal workpieces to obviate prior art shortcomings.

SUMMARY OF THE INVENTION

0007According to one aspect of the present invention, an apparatus for processing a sheet-metal workpiece includes a press tool having a bottom die and top die, a press having a platen for receiving the bottom die, and a ram for receiving the top die, and a protective system for the press tool, the protective system configured to detect an idle stroke and including an adjustable spacer assembly to prevent collision between the top and bottom dies.

0008The term “Idle stroke” relates in the description to a clamping or closing stroke, when no sheet-metal workpiece is placed between the bottom and top dies. The presence of such an idle stroke is unwanted because of the risk of collision between the bottom and top dies and can be caused, e.g., when the normal press operation malfunctions, during coil or blank stack change, or during set-up mode. The present invention addresses, i.a., this prior art problem by providing an active tool protective system which detects such idle strokes and thus prevents a collision of the bottom and top dies at the lowermost point of the closing motion (lower dead point). Thus, damage to the effective surface areas of the bottom and top dies, such as their die surface and ram surface, and in particular to their critical edges is prevented. The collision of the effective surface areas is prevented as a result of the presence of a mechanical distancing between the bottom and top dies, using the actively adjustable spacer assembly, which can also be referred to as distancing device.

0009The press tool may involve a forming tool and/or cutting tool.

0010According to another advantageous feature of the present invention, the spacer assembly can be arranged on the top die or the bottom die. Suitably, the spacer assembly can be attached to any rigid and immobile main tool component. The spacer assembly may also be arranged on the platen or ram. Depending on the arrangement, the spacer assembly may thus be effective between top die and bottom die, between platen and upper die, between bottom die and ram, or between platen and ram.

0011According to another advantageous feature of the present invention, the press tool or the press can have a sensor to ascertain the presence of a sheet-metal workpiece. Such a sensor provides information as to whether a sheet-metal workpiece is placed in the press tool during the actual clamping or working stroke. This information may also be provided by a press control (e.g. through querying initiators) to a preceding work station, a transfer or handling system etc.

0012According to another advantageous feature of the present invention, the protective system can include a control device configured to control the spacer assembly in response to a presence of a sheet-metal work piece in the press tool. The control device may, for example, operate an adjustment element that can move in or move out, or maintain a predefined distance of the adjustment element by causing the adjustment element to move in or move out a certain distance. The control device may be operably connected to an aforementioned sensor that can be installed in the press tool and forms a component of a press control, system control, or the like. Information transmitted by the sensor to the control device is processed by the control device, e.g. using a software algorithm. Advantageously, any required adjustment of the spacer assembly is established unencumbered between the working strokes. In the presence of several spacer assemblies, provision may be made to control and adjust the spacer assemblies in synchronism or also separately.

0013According to another advantageous feature of the present invention, several adjustable spacer assemblies can be provided to prevent the collision between the top and bottom dies in the presence of the idle stroke and to establish distance keepers during normal working stroke, i.e. in the presence of a sheet-metal workpiece. As a result, not only is a collision between the bottom and top dies avoided, but since the spacer assemblies are adjustable and thus not rigid, the pressing force upon the spacer assemblies is reduced, when the press tool, e.g. a forming tool, is run in, while still being able to maintain proper distance between the bottom and top dies or their effective surface areas in the lower dead point, so as to ensure the quality of the structure.

0014Advantageously, the spacer assemblies can include adjustment elements that can move in or move out. In this way, there is the possibility to move the adjustment elements out according to need, in part or in their entirety, to realize a certain distance. Otherwise the space assemblies assume the retracted position, so as to remove the space assemblies from the force flux or force transmission path. This means that the exposure to the pressing force can be reduced by up to 40% and more. The adjustable spacer assemblies may thus assume, if need be and when correspondingly configured, the function of a distance keeper to ensure a reliable and adjustable distance between the bottom and top dies or their effective surface areas and thus to ensure the quality of the workpiece being formed.

0015According to another aspect of the present invention, an adjustable spacer assembly for installation in an apparatus for processing a sheet-metal workpiece includes an adjustment element adapted to move in and out, a spring element applying a spring force to maintain the adjustment element under tension in a move-out direction, and a drive element to move the adjustment element in opposition to the spring force applied by the spring element.

0016In accordance with the present invention, the adjustment element (or pressure-exerting element) to effect the distance between the bottom and top dies is maintained under tension so as to seek the move-out position, so that the bottom and top dies of the press tool are automatically protected against collision in the event of a power loss, e.g. when an electric or pneumatic supply fails. Using the drive element enables the adjustment element to retract in opposition to the spring force in its entirety or also in part.

0017According to another advantageous feature of the present invention, the spacer assembly can include a drive mechanism which is arranged in the force flux or force transmission path between the drive element and the adjustment element and which can be configured self-locking so as to prevent the adjustment element from being excessively pushed in by the drive mechanism.

0018According to another advantageous feature of the present invention, the drive mechanism can include a wedge slide having a slanted surface bearing against a matching surface of the adjustment element so as to move the adjustment element in a vertical direction as the wedge slide is moved in a horizontal direction.

0019According to another advantageous feature of the present invention, a force sensor may be provided for force measurement. Force measurement is intended to ascertain a force applied in the idle stroke and, optionally, also in the working stroke, upon the adjustment element and thus the force transmitted from the spacer assembly. The ascertained force can be used for monitoring and, optionally, for readjustment or control of the adjustment element position. In addition, position transducer may also be provided to ascertain a position of the wedge slide and/or the adjustment element.

BRIEF DESCRIPTION OF THE DRAWING

0020Other features and advantages of the present invention will be more readily apparent upon reading the following description of currently preferred exemplified embodiments of the invention with reference to the accompanying drawing, in which:

0021<figref idref="DRAWINGS">FIG. 1</figref> is a schematic illustration of an apparatus for processing a sheet-metal workpiece in accordance with the present invention; and

0022<figref idref="DRAWINGS">FIG. 2</figref> is a cross sectional view of a spacer assembly installed in the apparatus of <figref idref="DRAWINGS">FIG. 1</figref>.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

0023Throughout all the figures, same or corresponding elements may generally be indicated by same reference numerals. These depicted embodiments are to be understood as illustrative of the invention and not as limiting in any way. It should also be understood that the figures are not necessarily to scale and that the embodiments may be illustrated by graphic symbols, phantom lines, diagrammatic representations and fragmentary views. In certain instances, details which are not necessary for an understanding of the present invention or which render other details difficult to perceive may have been omitted.

0024Turning now to the drawing, and in particular to <figref idref="DRAWINGS">FIG. 1</figref>, there is shown a schematic illustration of an apparatus for processing a sheet-metal workpiece M in accordance with the present invention, generally designated by reference numeral <b>1</b>. The apparatus <b>1</b> includes a press <b>100</b>, shown only schematically and including a platen <b>110</b> and a ram <b>120</b> structured to move in a vertical direction. The press <b>100</b> has a work space in which a press tool <b>200</b> is situated. The press tool <b>200</b> includes a bottom die <b>210</b> and a top die <b>220</b>. The bottom die <b>210</b> is arranged on the platen <b>110</b> and the top die <b>220</b> is secured to the ram <b>120</b>. The press tool involves, for example, a sheet-metal forming tool with a downholder or sheet-metal holder <b>230</b> arranged in the top die <b>220</b> for example. As the ram <b>120</b> is lowered (closing stroke), the sheet-metal workpiece M, located between the bottom die <b>210</b> and top die <b>220</b>, is shaped. The bottom die <b>210</b> has an effective surface area <b>215</b> and the top die <b>220</b> has an effective surface area <b>225</b>.

0025To avoid a collision between the bottom die <b>210</b> and top die <b>220</b> during an idle stroke, i.e. a closing stroke in the absence of a sheet-metal workpiece M and thereby prevent damage to the effective surface areas <b>215</b>, <b>225</b>, the apparatus <b>1</b> includes an active protective system having a sensor <b>310</b> and a control device <b>330</b> (<figref idref="DRAWINGS">FIG. 2</figref>) to detect the presence or absence of a sheet-metal workpiece M and to maintain a distance between the bottom die <b>210</b> and top die <b>220</b> at the lower dead point of the ram movement by controlling operation of several adjustable spacer assemblies <b>320</b>, so as to prevent impact between the effective surface areas <b>215</b>, <b>225</b> of the bottom die <b>210</b> and top die <b>220</b>, respectively (If-Then function).

0026The spacer assemblies <b>320</b> can be arranged, for example, on a base body of the bottom die <b>210</b> or on a rigid structure of the bottom die <b>210</b>, and act directly against the base body of the top die <b>220</b> or rigid structure of the top die <b>220</b>. As described above, other options for attachment are, of course, also conceivable.

0027Referring now to <figref idref="DRAWINGS">FIG. 2</figref>, there is shown a cross sectional view of a spacer assembly <b>320</b> of the protective system. The spacer assembly <b>320</b> is configured as impact-resistant structure having components which are accommodated in a housing <b>321</b> or the like so as to be protected from ingress of dirt. The spacer assembly <b>320</b> includes a piston-like pressure-exerting piece or adjustment element <b>322</b> which can move in and out by a wedge slide <b>323</b>. The wedge slide <b>323</b> is moved by a wedge-slide mechanism to adjust the position of the adjustment element <b>322</b>. As the adjustment element <b>322</b> moves in and out, the wedge-slide mechanism effects a force transfer and movement transfer with change in direction, as indicated by the double arrows, i.e. as the wedge slide <b>323</b> moves in a horizontal direction, the adjustment element <b>322</b> is forced to move in a vertical direction. The spacer assembly <b>320</b> further includes a spring element <b>324</b> by which the wedge slide <b>323</b> is maintained under tension to urge the adjustment element <b>322</b> to a move-out position. The displacement of the wedge slide <b>323</b> is realized by a double-acting drive element <b>325</b> to actively move the wedge slide <b>323</b> in two directions. As an alternative, the wedge slide <b>323</b> may be also be operated by a single-action drive element to actively move the wedge slide <b>323</b> in opposition to the spring force applied by the spring element <b>324</b>, i.e. to move the wedge slide <b>323</b> back.

0028The spring element <b>324</b> may involve, e.g., a mechanical spring or gas pressure spring. The drive element <b>325</b> may involve, e.g., an electrically-operated or pneumatically-operated actuator. The opposing disposition of the spring element <b>324</b> and the drive element <b>325</b>, as shown in <figref idref="DRAWINGS">FIG. 2</figref>, is to be understood as merely by way of example. The spacer assembly <b>320</b> further includes guides and movement stops for the adjustment element <b>322</b> and for the wedge slide <b>323</b>. Reference numerals <b>326</b> and <b>327</b> designate a force measuring sensor for ascertaining a force (pressure force) acting on the spacer assembly <b>320</b>, and a position transducer for ascertaining the position of the wedge slide <b>323</b> and the adjustment element <b>322</b>. The spacer assembly <b>320</b> may, of course, also include a plurality of adjustment elements <b>322</b>, spring elements <b>324</b> and/or drive elements <b>325</b>.

0029During normal operation of the press <b>100</b>, the adjustment element <b>322</b> of each spacer assembly <b>320</b> assumes the retracted position, i.e. has moved in. As soon as the sensor <b>310</b>, installed in the press tool <b>200</b>, detects in an idle stroke the absence of a sheet-metal workpiece M between the bottom die <b>210</b> and top die <b>220</b>, the adjustment element <b>322</b> is dynamically moved out actively by the drive element <b>325</b> with the assistance of the spring element <b>324</b> and forms a mechanical stop far the top die <b>220</b> so that a collision between the bottom die <b>210</b> and the top die <b>220</b> is prevented (active protection function). The pressing force is then transmitted via the spacer assemblies <b>320</b> and not via the effective surface areas <b>215</b>, <b>225</b>. Evaluation of the sensor signal from the tool sensor <b>310</b> and the operation of the drive elements <b>324</b> of the sensor assemblies <b>320</b> are executed by the control device <b>330</b>. As soon as a sheet-metal workpiece NA is disposed between the bottom die <b>210</b> and top die <b>220</b>, the adjustment elements <b>322</b> are retracted again. Each spacer assembly <b>320</b> is able to absorb great forces or pressing forces. The mechanism for the wedge slide <b>323</b> is self-locking to prevent the extended adjustment elements <b>322</b> from being pushed in by the top die <b>220</b>.

0030Due to the spring force applied by the spring element <b>324</b> upon the wedge slide <b>323</b>, the adjustment element <b>322</b> is spontaneously urged to move out as soon as the power supply to the spacer assembly <b>320</b> is cut. As a result, the bottom die <b>210</b> and top die <b>220</b> are automatically protected against colliding in the absence of a power supply (passive protection function).

0031Advantageously, each spacer assembly <b>320</b> is configured such that the adjustment element <b>322</b> can be moved not only between a retracted position and an extended position, but any intermediate position may also be assumed. The spacer assembly <b>320</b> can therefore also be used as vertically-adjustable distance keepers, as described above. Control of the spacer assembly <b>320</b> may also be implemented by the control device <b>330</b> as a function of measurement data provided by the force measuring sensor <b>326</b> and the position transducer <b>327</b>.

0032While the invention has been illustrated and described in connection with currently preferred embodiments shown and described in detail, it is not intended to be limited to the details shown since various modifications and structural changes may be made without departing in any way from the spirit and scope of the present invention. The embodiments were chosen and described in order to explain the principles of the invention and practical application to thereby enable a person skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated.

0033What is claimed as new and desired to be protected by Letters Patent is set forth in the appended claims and includes equivalents of the elements recited therein.